fix(coverage): v8 to ignore Vite's generated cjs import helpers

packages/coverage-v8/src/provider.ts

@@ -244,6 +244,20 @@ export class V8CoverageProvider extends BaseCoverageProvider<ResolvedCoverageOpt
           return true
         }
 
+        // CJS imports as ternaries - e.g.
+        // const React = __vite__cjsImport0_react.__esModule ? __vite__cjsImport0_react.default : __vite__cjsImport0_react;
+        if (
+          type === 'branch'
+          && node.type === 'ConditionalExpression'
+          && node.test.type === 'MemberExpression'
+          && node.test.object.type === 'Identifier'
+          && node.test.object.name.startsWith('__vite__cjsImport')
+          && node.test.property.type === 'Identifier'
+          && node.test.property.name === '__esModule'
+        ) {
+          return true
+        }
+
         // in-source test with "if (import.meta.vitest)"
         if (
           (type === 'branch' || type === 'statement')

test/coverage-test/fixtures/src/cjs-dependency.ts

@@ -0,0 +1,6 @@
+// @ts-expect-error -- types not picked up for some reason
+import cjsDefault from '@vitest/cjs-lib'
+
+export default function getA() {
+  return cjsDefault.a
+}

test/coverage-test/fixtures/test/cjs-dependency.test.ts

@@ -0,0 +1,6 @@
+import { test } from "vitest";
+import cjsDependency from "../src/cjs-dependency";
+
+test("cjs dependency vite transforms", () => {
+  cjsDependency()
+})

test/coverage-test/package.json

@@ -11,6 +11,7 @@
     "@types/istanbul-lib-report": "catalog:",
     "@vitejs/plugin-vue": "latest",
     "@vitest/browser-playwright": "workspace:*",
+    "@vitest/cjs-lib": "file:../browser/cjs-lib",
     "@vitest/coverage-istanbul": "workspace:*",
     "@vitest/coverage-v8": "workspace:*",
     "@vitest/web-worker": "workspace:*",

test/coverage-test/test/cjs-dependency.test.ts

@@ -0,0 +1,25 @@
+import { expect } from 'vitest'
+import { readCoverageMap, runVitest, test } from '../utils'
+
+test('excludes Vite transforms done for CJS dependency', async () => {
+  await runVitest({
+    include: ['fixtures/test/cjs-dependency.test.ts'],
+    coverage: {
+      reporter: 'json',
+    },
+  })
+  const coverageMap = await readCoverageMap()
+  const files = coverageMap.files()
+
+  expect(files).toMatchInlineSnapshot(`
+    [
+      "<process-cwd>/fixtures/src/cjs-dependency.ts",
+    ]
+  `)
+
+  const fileCoverage = coverageMap.fileCoverageFor('<process-cwd>/fixtures/src/cjs-dependency.ts')
+
+  // There should be 0 branches (#8717)
+  expect(Object.keys(fileCoverage.b)).toHaveLength(0)
+  expect(Object.keys(fileCoverage.branchMap)).toHaveLength(0)
+})

test/coverage-test/vitest.config.ts

@@ -87,6 +87,7 @@ export default defineConfig({
             '**/vue.test.ts',
             '**/in-source.test.ts',
             '**/query-param-transforms.test.ts',
+            '**/test/cjs-dependency.test.ts',
           ],
         },
       },
@@ -115,6 +116,7 @@ export default defineConfig({
             '**/vue.test.ts',
             '**/in-source.test.ts',
             '**/query-param-transforms.test.ts',
+            '**/test/cjs-dependency.test.ts',
           ],
         },
       },